Electrical problem, not alternator
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Electrical problem, not alternator
I thought the alternator went on my 99f150, 5.4ltr. I changed it and the same symptoms appear- it can be jumped, will show a charge but after warming for 5 minutes or less all the electrical, gages, power windows, lights, you name it go out. I figure it must be a short but.....any ideas?
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Alternator/short/temper update
The battery is only 10 months old and does hold a charge. If I let the truck sit and "cool down" it starts right up without a recharge, then this sequence begins after running 1-2 minutes:
1. The ampmeter on the dash begins to "tick down", several incremental drops until it is in the red. It starts above the midline.
2. The dash, dome and exterior lights begin to dim, slowly.
3. Last, all gages go to "zero" and lights go out while the truck still runs.
4. At this point I can turn it off, wait an hour, start it and watch it repeat the cycle.
The alternator was new, not rebuilt. I assume that it must function because of how the ampmeter on the dash shows it charging good and strong for the first minute. I have checked, rechecked and prayed over the connections.
This problem started abruptly, this makes me think maybe a short or broken cable, but the sequence of events and how predictable the repeat themselves makes me think a relay or something in the electrical system
At 120,000 miles this is just broken in, where do I tickle it to make it go?
1. The ampmeter on the dash begins to "tick down", several incremental drops until it is in the red. It starts above the midline.
2. The dash, dome and exterior lights begin to dim, slowly.
3. Last, all gages go to "zero" and lights go out while the truck still runs.
4. At this point I can turn it off, wait an hour, start it and watch it repeat the cycle.
The alternator was new, not rebuilt. I assume that it must function because of how the ampmeter on the dash shows it charging good and strong for the first minute. I have checked, rechecked and prayed over the connections.
This problem started abruptly, this makes me think maybe a short or broken cable, but the sequence of events and how predictable the repeat themselves makes me think a relay or something in the electrical system
At 120,000 miles this is just broken in, where do I tickle it to make it go?
Hotshot
Joined: Jul 2005
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the volt meter should not tick down. alternator can put out over 100 amps if needed. i wonder if the regulator is kicking out after a couple minutes and you are reading battery voltage only. if you had a short that big, something would be red hot after 2 minutes??
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That's just it, I'd think it would be a "sparks all over" short. I found the following thread
-----------------------------------------------------------------------------------
Alternator check for F150
C1 CHECK FOR OPEN A CIRCUIT
* Measure voltage at test point A on the voltage regulator.
* Is voltage at test point A equal to battery voltage?
Yes
GO to «C2».
No
CHECK fuse in Circuit 36 (Y/W) and REPLACE if required. If OK, SERVICE open in Circuit 36 (Y/W).
---------------------------------------------------------------------------------
I did this check, I think the diagram that goes with this ( that will not copy to this email) is from a service manual. Anyway, in checking test point A I get only .2volts. My question would be where is the fuse in circuit 36?
Or, I am off track here?
-----------------------------------------------------------------------------------
Alternator check for F150
C1 CHECK FOR OPEN A CIRCUIT
* Measure voltage at test point A on the voltage regulator.
* Is voltage at test point A equal to battery voltage?
Yes
GO to «C2».
No
CHECK fuse in Circuit 36 (Y/W) and REPLACE if required. If OK, SERVICE open in Circuit 36 (Y/W).
---------------------------------------------------------------------------------
I did this check, I think the diagram that goes with this ( that will not copy to this email) is from a service manual. Anyway, in checking test point A I get only .2volts. My question would be where is the fuse in circuit 36?
Or, I am off track here?
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Ding Ding Ding
I think I got it, need to get on the scooter for a new 20amp fuse. My checks (reading threads) kept going back to fuse 11 under the hood. Looked perfect, checked it 3 times yesterday. Today I was frustrated to the point of actually checking continuity......it was open. Never saw this before but it was cracked near the inside edge. If I twisted the fuse it showed the break. I hope this is it...will let you know for sure.
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A bad fuse is a bad fuse. This one was fractured, not burned, that was the odd part. I've already put 250 miles on it since installing the new fuse and its running like a champ, charging the battery as it should.
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